The genetic etiology of prostate cancer, the most common cancer in western men, is poorly understood. Highest incidences and mortality rates are reported for African-Americans, with 1.6x more likely than European-Americans and 2.6x more likely than Asian-Americans to develop disease. This ethnic disparity and a strong link to a family history of disease, eludes to the importance of genetics in explaining the observed health disparity (including disease risk, aggression and outcomes). We report for the first time a highly significant increase in disease aggression in non-migrant Africa, compared with African-Americans and European-Americans, and hypothesize that a genetic link to Africa plays a fundamental role in unraveling the prostate cancer disparities. The mitochondrial genome is not only a critical target for inherited disparity (due to ethnic-based diversity, which is greatest wihin Africa), but is also an important target for acquired tumor-causing somatic mutations. Mitochondria play a central role not only in generating cellular energy, but also cell death (apoptosis), cell growth and differentiation, signaling and cell cycle control, making the mitochondrial genome an essential target for carcinogenic variation. The high mutation rate and copy number of the mitochondrial compared to the nuclear genome, further impacts on its unique potential for pathogenesis and as a disease marker. This project will provide the first known analysis of the role and extent of acquired mitochondrial genome variation (somatic mutations with functional predictive relevance) on a backbone of inherited variation (polymorphic variants) in defining the increased severity of prostate cancer within Africa. Using a unique study resource of non-admixed Southern African ancestry, combined with whole mitochondrial genome analysis using next generation sequencing technology, will provide an opportunity to identify genetic-based non- invasive biomarkers of aggressive versus indolent prostate cancer disease (a major clinical limitation in the management of prostate cancer), as well as the tools to detect low levels of somatic heteroplasmy (mutant to wild-type mtDNA environment) for early-disease detection and monitoring. This study addresses an important biological explanation for the observed ethnic- based disparities in prostate cancer.